This study will examine the effects of long-term adherence to a low protein diet (LPD) of 0.6 g/kg-1/d-1 with and without progressive resistance exercise training in patients with impaired renal function on body composition, renal function (glomerular filtration rate), nitrogen balance, muscle strength and size, and functional capacity. The hypothesis is that adherence to a LPD will result in a reduction in skeletal muscle mass and reduced strength and functional capacity while those patients who adhere to the LPD and exercise will demonstrate a similar preservation of renal function but will have greater fat free mass, muscle mass and strength. The intervention trial will last 18 months in which patients with moderate renal failure will be randomly assigned to one of 4 interventions: standard care, standard care + exercise, LPD, and LPD with exercise. In this way the independent and combined effects of diet and exercise on the progression of renal disease and body composition will be monitored. This study will have important implications for the treatment of patients with chronic renal failure. New strategies of combining exercise with recommendations of a low protein diet may slow the progression of renal disease and improve strength and functional capacity in these at-risk patients.